Summer can be a particularly bad time for skin allergies such as eczema and hives, as well as reactions to poison ivy, oak and sumac, an expert says.

This summer, high rainfall, humidity and temperatures combined with increased levels of carbon dioxide in the air have resulted in an "exceedingly potent" growth of poison ivy-related plants, said Dr.

Leonard Bielory, an allergy specialist with the Rutgers Center of Environmental Prediction and an attending physician at Robert Wood Johnson University Hospital in New Brunswick, N.J.

"When picnicking or hiking though our parks this summer, beware of certain plants, especially some trees," he said in a hospital news release. "Many trees have leaves that are actually part of the (allergenic plant) vines that have embraced them."

Some of these allergenic plant vines are extremely large and clearly noticeable, said Bielory, recalling the saying that helps people avoid these troublesome plants: "Leaves of three, let them be."

Bielory added: "Some individuals are sensitive to the point that their conditions can flare up when in contact with grass or other plants. For protection, wear long pants and long sleeves if outdoor plants cause a reaction."

He also offered tips to prevent eczema and hives or at least reduce their symptoms:

Be careful when outdoors. Heat or sweat can trigger hives. Drink plenty of fluids, avoid becoming too hot and use sunscreen.Be prepared. Eczema can get worse in the summer, especially with added sweating. Have a skin care treatment plan. This may include using mild bathing products.